DESCRIPTION: Staphylococcus aureus is a major cause of a bacterial keratitis that often involves intense pain, extensive ocular inflammation, corneal scarring, and loss of visual acuity. Antibiotic therapy administered repeatedly over several days will kill the bacteria, however, no present therapy can prevent the corneal scarring associated with staphylococcal keratitis. The PI has studied experimental bacterial keratitis extensively and is dedicated to the long term goal of developing chemotherapy and immunotherapy for bacterial keratitis that will not only kill the bacteria, but also inhibit the effects of bacterial proteins (toxins/enzymes) and inhibit the host reactions that result in corneal scarring. These studies are designed to identify staphylococcal proteins and host reactions that mediate corneal scarring. Inhibitors of these reactions have the potential to evolve into new therapies that, when combined with antibiotics, could arrest corneal damage and sterilize the cornea. The specific aims are: 1) to identify the specific staphylococcal proteins (toxins/enzymes) necessary for corneal damage, and 2) to determine the role of key host factors in corneal damage. To identify staphylococcal proteins responsible for corneal damage, he will a:) determine the virulence of presently available Staphylococcus mutants deficient in specific toxins or enzymes relative to that of the virulent, isogenic parent strain; b) evaluate the direct effects of purified staphylococcal proteins injected into normal cornea; and c) confirm the role of specific proteins in corneal virulence using plasmids coding for a single staphylococcal protein to augment the virulence of mutants deficient in that protein (genetic rescue experiment). For identification of host factors that contribute to or limit corneal pathogenesis and damage, parent and mutant Staphylococcus strains will be employed to determine the roles in tissue damage of: a)corneal matrix metalloproteinases, and b) anti-staphylococcal antibodies. Identification of both bacterial and host mediators of corneal damage will reveal possible targets for future therapies designed to reduce corneal damage. The ultimate goal is to identify a therapeutic regimen that sterilizes the cornea and prevents or arrests corneal scarring.